The AX88772B uses only 11 bits of the header for the actual size. The other bits
are used for something else. This causes dmesg full of messages:

	asix_rx_fixup() Bad Header Length

This patch trims the check to only 11 bits. I believe on older chips, the
remaining 5 top bits are unused.

Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>